For some bachelorettes, an anti-Valentine's party consists of sipping a bottle of red, popping a Vicodin, and floating into the arms of the Oxygen network. For the rugged bachelor, a six-pack of Bud, ESPN, and an Internet porn nightcap is sufficient. Yet the more adventurous (crazy? desperate? undersexed? future Peter Braunsteiners?) opt to attend singles parties for Valentine's Day, possibly the darkest day of the yearsecond only to December 25, April 15, and September 11. Dewey's Flatiron, a cozy after-work tavern, hosts its eighth annual AntiValentine's Day bash (admission $10) on Saturday at 9:30 p.m.: a singles meet-and-greet, horndoggedly fueled by drink specials and an '80s DJ. Plus free roses and chocolates for the ladies. Put the loony-farm paddy wagons on standbyallegedly this mother's always packed?! Dunno about soul mate scouting, but for killer happy-hour beer specials (weekdays from 4 to 7, $3.50), a decent tap selection (Harp, Paulaner Hef, Pilsner Urquell, $6.50), tasty apple martinis (Friday's $5-martini night), pool, and high-caliber bar food (cheesesteak = trés yum, $9), Dewey's is a great place to kick it with the co-workers. Dug the loungey, mansion library cum fancy train station depot feel of the place, which is ornamented with wrought iron and wood and den-like leather couches. But the orgy of TVs (sports-o-rama!) lowbrows the vaulted-brick-ceiling-and-red-velvet-curtain charm. Granted, methinks the aim here's primarily post-office chill-out, not cushy Campbell Apartmentlike ambiencethat's too bad, they almost have both.